1. Field of the Invention
This invention relates generally to shuttleless looms and more particularly to a driving mechanism for selvage forming knitting needles in shuttleless looms.
2. Prior Art
Shuttleless looms have been known in which loops of weft yarn are successively inserted into the warp sheds by means of a weft inserting finger and are interknitted at one edge of the fabric by a selvage forming knitting needle. In looms of this type, both the weft inserting finger and the knitting needle perform a reciprocating motion in one plane and cross each other where the successive weft loops are interknitted in an extremely short period of time, when the knitting needle tends to miss the next loop of weft yarn. One solution to the above problem has been to move the knitting needle up and down to ensure that the knitting needle engage the weft thread without fail.
For example, an attempt has been made to cause the knitting needle to follow an arcuate or a substantially arcuate path during its back-and-forth reciprocating movement, which path lies in a vertical plane extending in a crisscross relation to a horizontal plane in which the weft inserting finger sweeps through the warp shed. This attempt has avoided the missing of the next loop of weft yarn but has produced a relatively large and loose knitted selvage, since the previous loop which remains engaged on the shank of the knitting needle moves also up and down and becomes enlarged at a position adjacent to the fell of the fabric on account of the arcuate movement of the knitting needle.
It has been therefore been suggested that the knitting needle be arranged to perform a substantially straight motion near the fell, without preventing the engagement of the ensuing weft loop with the knitting needle. One such attempt has been to arrange the knitting needle in order to carry out a combined arcuate and substantially straight motion so that the up-and-down movement of the needle shank near the fell will be held to a minimum during the reciprocating motion of the knitting needle. Another attempt has employed a mechanism whereby the advancing movement of the knitting needle can be effected in a path different from that in which its retracting movement is effected in order to minimize the up-and-down movement of the needle shank adjacent to the fabric fell.
With these prior attempts, however, the needle shank is still prone to move up and down during its reciprocation and, in addition, the power transmission mechanism must be equipped with a slide member for reciprocating the knitting needle. This slide member itself causes an additional problem in that the loops of weft yarn are susceptible to missing by the knitting needle because the slide member gets worn during its reciprocating movement and cannot move accurately where desired. Furthermore, the slide member must be supplied with an oil to provide proper lubrication which oil then tends to be scattered about and deposited on the yarns and the fabric which is being woven. The slide member presents still another difficulty in that the slide member, being in most cases located adjacent to the fabric fell, takes up space and makes it difficult to adjust the position of, or replace the knitting needle and to thread the weft inserting finger and the reed.